STT-MRAM design enhanced by switching current induced magnetic field

ABSTRACT

A memory cell includes an elongated first electrode coupled to a magnetic tunnel junction (MTJ) structure and an elongated second electrode aligned with the elongated first electrode coupled to the MTJ structure. The elongated electrodes are configured to direct mutually additive portions of a switching current induced magnetic field through the MTJ. The mutually additive portions enhance switching of the MTJ in response to application of the switching current.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 13/770,306, filed on Feb. 19, 2013, and entitled “STT-MRAM DESIGNENHANCED BY SWITCHING CURRENT INDUCED MAGNETIC FIELD,” the disclosure ofwhich is expressly incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure generally relates to magnetic random accessmemory (MRAM) devices. More specifically, the present disclosure relatesto a design for spin transfer torque (STT) MRAM devices that areenhanced by a spin-transfer torque switching current induced magneticfield.

BACKGROUND

Unlike conventional random access memory (RAM) chip technologies, inmagnetic RAM (MRAM) data is not stored as electric charge, but isinstead stored by magnetic polarization of storage elements. The storageelements are formed from two ferromagnetic layers separated by atunneling layer. One of the two ferromagnetic layers, which is referredto as the fixed layer or pinned layer, has a magnetization that is fixedin a particular direction. The other ferromagnetic magnetic layer, whichis referred to as the free layer, has a magnetization direction that canbe altered to represent either a “1” when the free layer magnetizationis anti-parallel to the fixed layer magnetization or “0” when the freelayer magnetization is parallel to the fixed layer magnetization or viceversa. One such device having a fixed layer, a tunneling layer, and afree layer is a magnetic tunnel junction (MTJ). The electricalresistance of an MTJ depends on whether the free layer magnetization andfixed layer magnetization are parallel or anti-parallel with each other.A memory device such as MRAM is built from an array of individuallyaddressable MTJs.

To write data in a conventional MRAM, a write current, which exceeds acritical switching current, is applied through an MTJ. The write currentexceeding the critical switching current is sufficient to change themagnetization direction of the free layer. When the write current flowsin a first direction, the MTJ can be placed into or remain in a firststate, in which its free layer magnetization direction and fixed layermagnetization direction are aligned in a parallel orientation. When thewrite current flows in a second direction, opposite to the firstdirection, the MTJ can be placed into or remain in a second state, inwhich its free layer magnetization and fixed layer magnetization are inan anti-parallel orientation.

To read data in a conventional MRAM, a read current may flow through theMTJ via the same current path used to write data in the MTJ. If themagnetizations of the MTJ's free layer and fixed layer are orientedparallel to each other, the MTJ presents a resistance that is differentthan the resistance the MTJ would present if the magnetizations of thefree layer and the fixed layer were in an anti-parallel orientation. Ina conventional MRAM, two distinct states are defined by two differentresistances of an MTJ in a bitcell of the MRAM. The two differentresistances represent a logic 0 and a logic 1 value stored by the MTJ.

To determine whether data in a conventional MRAM represents a logic 1 ora logic 0, the resistance of the MTJ in the bitcell is compared with areference resistance. The reference resistance in conventional MRAMcircuitry is a midpoint resistance between the resistance of an MTJhaving a parallel magnetic orientation and an MTJ having ananti-parallel magnetic orientation. One way of generating a midpointreference resistance is coupling in parallel an MTJ known to have aparallel magnetic orientation and an MTJ known to have an anti-parallelmagnetic orientation.

Bitcells of a magnetic random access memory may be arranged in one ormore arrays including a pattern of memory elements (e.g., MTJs in caseof MRAM). STT-MRAM (Spin-Transfer-Torque Magnetic Random Access Memory)is an emerging nonvolatile memory that has advantages of non-volatility,comparable speed to eDRAM (Embedded Dynamic Random Access Memory),smaller chip size compared to eSRAM (Embedded Static Random AccessMemory), unlimited read/write endurance, and low array leakage current.

SUMMARY

According to an aspect of the present disclosure, a memory cell has aset of magnetic tunnel junction (MTJ) layers. The set of MTJ layersincludes a fixed layer, a free layer and a barrier layer between thefixed layer and the free layer. The memory cell also includes a firstelectrode coupled to a first one of the MTJ layers. The first electrodeincludes a first elongated portion extending laterally away from the MTJlayers. The memory cell also includes a second electrode coupled to asecond one of the MTJ layers. The second electrode includes a secondelongated portion extending laterally away from the MTJ layers. Thefirst elongated portion is configured to direct a first portion of amagnetic field induced by an MTJ switching current through the MTJlayers. The second elongated portion is configured to direct a secondportion of the magnetic field induced by the MTJ switching currentthrough the MTJ layers. According to aspects of the present disclosure,the second portion of the magnetic field adds with the first portion ofthe magnetic field to enhance the magnetic field through the MTJ layers.

According to another aspect of the present disclosure, a method ofconstructing a magnetic memory cell includes patterning a firstelectrode. The method also includes fabricating an MTJ on the firstelectrode so that the first electrode has a first elongated portionextending laterally away from the MTJ. The method further includespatterning a second electrode on the MTJ so that the second electrodehas a second elongated portion extending laterally away from the MTJ.The method also includes configuring the first elongated portion and thesecond elongated portion to direct mutually additive portions of aswitching current induced magnetic field through the MTJ.

Another aspect of the present disclosure includes an apparatus thatincludes a means for magnetically storing charge, a first means forconducting and a second means for conducting. The means for magneticallystoring charge has a set of layers, the set of layers including a fixedlayer, a free layer and a barrier layer between the fixed layer and thefree layer. The first means for conducting is coupled to a first one ofthe set of layers of the means for magnetically storing charge. Thefirst means for conducting also includes a first means for directing amagnetic field that extends laterally away from the means formagnetically storing charge. The first means for directing a magneticfield is configured to direct a first portion of a magnetic fieldinduced by a switching current through the means for magneticallystoring charge. The second means for conducting is coupled to a secondone of the set of layers of the means for magnetically storing charge.The second means for conducting also includes a second means fordirecting magnetic field that extends laterally away from the means formagnetically storing charge. The second means for directing magneticfield is configured to direct a second portion of the magnetic fieldinduced by the switching current through the means for magneticallystoring charge. The second portion of the magnetic field also adds withthe first portion of the magnetic field to enhance the magnetic fieldthrough the means for magnetically storing charge.

This has outlined, rather broadly, the features and technical advantagesof the present disclosure in order that the detailed description thatfollows may be better understood. Additional features and advantages ofthe disclosure will be described below. It should be appreciated bythose skilled in the art that this disclosure may be readily utilized asa basis for modifying or designing other structures for carrying out thesame purposes of the present disclosure. It should also be realized bythose skilled in the art that such equivalent constructions do notdepart from the teachings of the disclosure as set forth in the appendedclaims. The novel features, which are believed to be characteristic ofthe disclosure, both as to its organization and method of operation,together with further objects and advantages, will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, referenceis now made to the following description taken in conjunction with theaccompanying drawings.

FIG. 1 is a block diagram of a conventional STT-MRAM design.

FIG. 2A is a block diagram of an STT-MRAM according to an aspect of thepresent disclosure.

FIG. 2B is a top view diagram of an STT-MRAM according to an aspect ofthe present disclosure.

FIG. 3A is a block diagram of an STT-MRAM according to an aspect of thepresent disclosure.

FIG. 3B is a top view diagram of STT-MRAM according to an aspect of thepresent disclosure.

FIG. 4A is a block diagram of an STT-MRAM according to an aspect of thepresent disclosure.

FIG. 4B is a top view diagram of an STT-MRAM according to an aspect ofthe present disclosure.

FIG. 5 is a performance graph illustrating switching time versusswitching current for an STT-MRAM design according to an aspect of thepresent disclosure.

FIG. 6 is a process flow diagram illustrating a method of constructingan STT-MRAM according to an aspect of the present disclosure.

FIG. 7 is a block diagram showing an exemplary wireless communicationsystem in which a configuration of the disclosure may be advantageouslyemployed.

FIG. 8 is a block diagram illustrating a design workstation used forcircuit, layout, and logic design of a semiconductor component accordingto one configuration.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a conventional spin transfer torquemagnetic random access memory (STT-MRAM) 100. The conventional MRAMstructure 100 includes a magnetic tunnel junction (MTJ) 110 that has afirst ferromagnetic layer 107 a second ferromagnetic layer 109 and atunnel barrier layer 108 coupled between the first ferromagnetic layer107 and the second ferromagnetic layer 109. A top electrode 106 iscoupled to the first ferromagnetic layer 107 and a bottom electrode 112is coupled to the second ferromagnetic layer 109. A top conductive layer102 is coupled to the top electrode 106 by a conductive via 104. Abottom conductive layer 116 is coupled to the bottom electrode 112 by aconductive via 114. The first ferromagnetic layer 107 may be a fixedlayer and the second ferromagnetic layer 109 may be a free layer, forexample. In another implementation, the first ferromagnetic layer 107may be a free layer and the second ferromagnetic layer 109 may be afixed layer. The tunnel barrier layer 108 may be made from an insulatingmaterial, such as magnesium oxide MgO, for example.

FIG. 2A is a block diagram of an STT-MRAM 200 according to an aspect ofthe present disclosure. The STT-MRAM 200 includes an MTJ 210 thatincludes a top ferromagnetic layer 207, a bottom ferromagnetic layer 209and a tunnel barrier layer 208, coupled between the top ferromagneticlayer 207 and the bottom ferromagnetic layer 209. In one implementation,the top ferromagnetic layer 207 may be a free layer and the bottomferromagnetic layer 209 may be a fixed layer, for example. In anotherimplementation, the top ferromagnetic layer 207 may be a fixed layer andthe bottom ferromagnetic layer 209 may be a free layer. The tunnelbarrier layer 208 may be made from an insulating material, such as MgO,for example.

The top ferromagnetic layer 207 is coupled to a top electrode 206 andthe bottom ferromagnetic layer 209 is coupled to a bottom electrode 212.A top conductive layer 202, such as metal layer M5, is coupled to thetop electrode 206 by a top via 204 and a bottom conductive layer 216,such as metal layer M4, is coupled to the bottom electrode 212 by abottom via 214, also referred to as a contact.

According to an aspect of the present disclosure, the top conductivelayer 202 and bottom conductive layer 216 are laterally offset from theMTJ 210. The top electrode 206 includes an elongated portion 205 thatextends laterally from the MTJ 210 to the top via 204. The bottomelectrode 212 also includes an elongated portion 211 that extendslaterally from the MTJ 210 to the bottom via 214.

FIG. 2B is a top view of the STT-MRAM structure 200 shown in FIG. 2A inwhich dotted lines denote hidden layers. For instance, in FIG. 2B, theMTJ 210 is hidden under the top electrode 206. The top via 204 and thebottom via 214 are hidden under the top conductive layer 202.

As can be seen in both FIG. 2A and FIG. 2B, the top electrode 206 andthe bottom electrode 212 are substantially aligned with each other. Theelongated portion 205 of the top electrode 206 is also substantiallyaligned with the elongated portion 211 of the bottom electrode 212. Aswitching current applied to the MTJ 210 flows along a current path fromthe top conductive layer 202 to the top electrode 206, through the MTJ210 to the bottom electrode 212 and then to the bottom conductive layer216. According to aspects of the present disclosure, the lateraldisplacement between the top conductive layer 202 and the MTJ 210 causesthe switching current to flow laterally, e.g., in a plane parallel tothe MTJ layers, in both the top electrode 206 and the bottom electrode212. A magnetic field is naturally induced around the current path bythe switching current when the switching current is applied to the MTJ210. As in a conventional MTJ configuration, the switching currenttraveling through the MTJ 210 from the top ferromagnetic layer 207 tothe bottom ferromagnetic layer 209 induces a first portion (H₁) (shownin FIG. 2B) of the magnetic field that circulates around the currentpath parallel to the planes of the MTJ layers 207, 208, 209.

According to aspects of the present disclosure, the switching currenttraveling in the top electrode 206 from the top via 204 to the MTJ 210induces a second portion (H₂) of the magnetic field that circulatesaround the switching current in the top electrode 206. It should beunderstood by persons having ordinary skill in the art that the secondportion H₂ of the magnetic field is directed through the MTJ 210 asshown by the magnetic field vector 201 in the direction shown in FIGS.2A and 2B.

According to aspects of the present disclosure, the switching currenttraveling in the bottom electrode 212 from the MTJ 210 to the bottom via214 induces a third portion (H₃) of the magnetic field that circulatesaround the current in the bottom electrode 212. It should be understoodby persons having ordinary skill in the art that the third portion H₃ ofthe magnetic field is directed through the MTJ 210 as shown by themagnetic field vector 203 in the direction shown in FIGS. 2A and 2B.

According to aspects of the present disclosure, the substantial mutualalignment (i.e., pattern) of elongated portions 205, 211 of the top andbottom electrodes causes the second portion H₂ of the magnetic field andthe third portion H₃ of the magnetic field to be mutually additive inone direction through the MTJ 210.

Persons having ordinary skill in the art should recognize that an axisof the MTJ that is aligned in the most energetically favorable directionof magnetization is generally referred to as the MTJ's “easy axis”. Forexample, an MTJ may be configured with an elliptical shape, in which theeasy axis of the MTJ 210 corresponds to a long axis of the ellipticalshape. In FIG. 2B, the MTJ 210 has a rectangular shape and the easy axisof the MTJ 210 corresponds to the long axis of the rectangular shape.

According to an aspect of the present disclosure, the top electrode 206and bottom electrode 212 are arranged so that the mutually additiveportions H₂ and H₃ of a magnetic field induced by a switching currentapplied to the MTJ 210 are directed through the MTJ 210 in a directionperpendicular to the MTJ's easy axis.

According to another aspect of the present disclosure described withreference to FIGS. 3A and 3B, the mutually additive portions H₂ and H₃of a magnetic field induced by a switching current applied to an MTJ maybe directed through the MTJ in a direction parallel to the MTJ's easyaxis. FIG. 3A is a block diagram of an STT-MRAM 300 according to anaspect of the present disclosure. The STT-MRAM 300 includes an MTJ 310that has a top ferromagnetic layer 307, a bottom ferromagnetic layer 309and a tunnel barrier layer 308, coupled between the top ferromagneticlayer 307 and the bottom ferromagnetic layer 309. In one implementation,the top ferromagnetic layer 307 may be a free layer and the bottomferromagnetic layer 309 may be a fixed layer, for example. In anotherimplementation, the top ferromagnetic layer 307 may be a fixed layer andthe bottom ferromagnetic layer 309 may be a free layer. The tunnelbarrier layer 308 may be made from an insulating material, such as MgO,for example.

The top ferromagnetic layer 307 is coupled to a top electrode 306 andthe bottom ferromagnetic layer 309 is coupled to a bottom electrode 312.A top conductive layer 302, such as metal layer M5, is coupled to thetop electrode 306 by a top via 304 and a bottom conductive layer 316,such as metal layer M4, is coupled to the bottom electrode 312 by abottom via 314, also referred to as a contact.

FIG. 3B is a top view of the STT-MRAM structure 300 shown in FIG. 3A inwhich dotted lines denote hidden layers. For instance, in FIG. 3B, theMTJ 310 is hidden under the top electrode 306. The top via 304 and thebottom via 314 are hidden under the top conductive layer 302.

As best seen in FIG. 3B, the top conductive layer 302 and bottomconductive layer 316 include portions that are laterally offset from theMTJ 310. The top electrode 306 includes an elongated portion 305 thatextends laterally from the MTJ 310 to the top via 304. The bottomelectrode 312 also includes an elongated portion 311 that extendslaterally from the MTJ 310 to the bottom via 314.

As can be seen in both FIG. 3A and FIG. 3B, the top electrode 306 andthe bottom electrode 312 are substantially aligned with each other. Theelongated portion 305 of the top electrode 306 is also substantiallyaligned with the elongated portion 311 of the bottom electrode 312. Aswitching current applied to the MTJ 310 flows along a current path fromthe top conductive layer 302 to the top electrode 306, through the MTJ310 to the bottom electrode 312 and then to the bottom conductive layer316. According to aspects of the present disclosure, the lateraldisplacement between the top conductive layer 302 and the MTJ 310 causesthe switching current to flow laterally, e.g., in a plane parallel tothe MTJ layers, in both the top electrode 306 and the bottom electrode312.

A magnetic field is naturally induced around the current path by theswitching current when the switching current is applied to the MTJ 310.As in a conventional MTJ configuration, the switching current travelingthrough the MTJ 310 from the top ferromagnetic layer 307 to the bottomferromagnetic layer 309 induces a first portion (H₁) (shown in FIG. 3B)of the magnetic field that circulates around the current path parallelto the planes of the MTJ layers 307, 308, 309.

According to aspects of the present disclosure, the switching currenttraveling in the top electrode 306 from the top via 304 to the MTJ 310induces a second portion (H₂) of the magnetic field that circulatesaround the switching current in the top electrode 306. It should beunderstood by persons having ordinary skill in the art that the secondportion H₂ of the magnetic field is directed through the MTJ 310 asshown by the magnetic field vector 301 in the direction shown in FIG.3B.

According to aspects of the present disclosure, the switching currenttraveling in the bottom electrode 312 from the MTJ 310 to the bottom via314 induces a third portion (H₃) of the magnetic field that circulatesaround the current in the bottom electrode 312. It should be understoodby persons having ordinary skill in the art that the third portion H₃ ofthe magnetic field is directed through the MTJ 310 as shown by themagnetic field vector 303 in the direction shown in FIGS. 3B.

According to aspects of the present disclosure, the substantial mutualalignment (i.e., pattern) of elongated portions 305, 311 of the top andbottom electrodes 306, 312 causes the second portion H₂ of the magneticfield and the third portion H₃ of the magnetic field to be mutuallyadditive in one direction through the MTJ 310 .

In FIG. 3B, the MTJ 310 has a rectangular shape and the easy axis of theMTJ 310 corresponds to the long axis of the rectangular shape. Accordingto an aspect of the present disclosure, the top electrode 306 and bottomelectrode 312 are arranged so that the mutually additive portions H₂ andH₃ of a magnetic field induced by a switching current applied to the MTJ310 are directed through the MTJ 310 in a direction parallel to theMTJ's easy axis.

The electrodes 306, 312 are designed to control the magnetic fieldinduced by the internal switching current more effectively. Thethickness of the electrodes 306, 312 can be increased by addition ofmore electrode material or by being combined with other conductivelayers (e.g., layers 302, 316 and other layers) in order to reduce thecurrent-resistance or IR drop across the STT-MRAM device. Therefore, theswitching time and the switching energy consumption are lowered, leadingto improved efficiency and performance.

According to another aspect of the present disclosure described withreference to FIGS. 4A and 4B, the mutually additive portions H₂ and H₃of a magnetic field induced by a switching current applied to an MTJ maybe directed through the MTJ at an angle to the MTJ's easy axis. FIG. 4Ais a block diagram of an STT-MRAM 400 according to an aspect of thepresent disclosure. The STT-MRAM 400 includes an MTJ 410 that includes atop ferromagnetic layer 407, a bottom ferromagnetic layer 409 and atunnel barrier layer 408, coupled between the top ferromagnetic layer407 and the bottom ferromagnetic layer 409. In one implementation, thetop ferromagnetic layer 407 may be a free layer and the bottomferromagnetic layer 409 may be a fixed layer, for example. In anotherimplementation, the top ferromagnetic layer 407 may be a may be a fixedlayer and the bottom ferromagnetic layer 409 may be a free layer. Thetunnel barrier layer 408 may be made from an insulating material, suchas MgO, for example.

The top ferromagnetic layer 407 is coupled to a top electrode 406 andthe bottom ferromagnetic layer 409 is coupled to a bottom electrode 412.A top conductive layer 402, such as metal layer M5, is coupled to thetop electrode 406 by a top via 404. A bottom conductive layer 416, suchas metal layer M4, is coupled to the bottom electrode 412 by a bottomvia 414, also referred to as a contact.

FIG. 4B is a top view of the STT-MRAM structure 400 shown in FIG. 4A inwhich dotted lines denote hidden layers. For instance, in FIG. 4B, theMTJ 410 is hidden under the top electrode 406. The top via 404 and thebottom via 414 are hidden under the top conductive layer 402.

As seen in FIG. 4B, the top conductive layer 402 and bottom conductivelayer 416 include portions laterally offset from the MTJ 410. The topelectrode 406 includes an elongated portion 405 that extends laterallyfrom the MTJ 410 to the top via 404. The bottom electrode 412 alsoincludes an elongated portion 411 that extends laterally from the MTJ410 to the bottom via 414.

The top electrode 406 and the bottom electrode 412 are substantiallyaligned with each other. The elongated portion 405 of the top electrode406 is also substantially aligned with the elongated portion 411 (shownin FIG. 4B) of the bottom electrode 412. A switching current applied tothe MTJ 410 flows along a current path from the top conductive layer 402to the top electrode 406, through the MTJ 410 to the bottom electrode412 and then to the bottom conductive layer 416. According to aspects ofthe present disclosure, the lateral displacement between the topconductive layer 402 and the MTJ 410 causes the switching current toflow laterally, e.g., in a plane parallel to the MTJ layers, in both thetop electrode 406 and the bottom electrode 412.

A magnetic field is naturally induced around the current path by theswitching current when the switching current is applied to the MTJ 410.As in a conventional MTJ configuration, the switching current travelingthrough the MTJ from the top ferromagnetic layer 407 to the bottomferromagnetic layer 409 induces a first portion (H₁) (shown in FIG. 4B)of the magnetic field that circulates around the current path parallelto the planes of the MTJ layers 407, 408, 409. According to aspects ofthe present disclosure, the switching current traveling in the topelectrode 406 from the top via 404 to the MTJ 410 induces a secondportion (H₂) of the magnetic field that circulates around the switchingcurrent in the top electrode 406. It should be understood by personshaving ordinary skill in the art that the second portion H₂ of themagnetic field is directed through the MTJ 410 as shown by the magneticfield vector 401 in the direction shown in FIGS. 4A and 4B.

According to aspects of the present disclosure, the switching currenttraveling in the bottom electrode 412 from the MTJ 410 to the bottom via414 induces a third portion (H₃) of the magnetic field that circulatesaround the current in the bottom electrode 412. It should be understoodby persons having ordinary skill in the art that the third portion H₃ ofthe magnetic field is directed through the MTJ 410 as shown by themagnetic field vector 403 in the direction shown in FIGS. 4A and 4B.

According to aspects of the present disclosure, the substantial mutualalignment (i.e., pattern) of elongated portions 405, 411 of the top andbottom electrodes 406, 412 causes the second portion H₂ of the magneticfield and the third portion H₃ of the magnetic field to be mutuallyadditive in one direction through the MTJ 410.

In FIG. 4B, the MTJ 410 has a rectangular shape and the easy axis of theMTJ 410 corresponds to the long axis of the rectangular shape. Accordingto an aspect of the present disclosure, the top electrode 406 and bottomelectrode 412 are arranged so that the mutually additive portions H₂ andH₃ of a magnetic field induced by a switching current applied to the MTJ410 are directed through the MTJ 410 at an angle relative to the MTJ'seasy axis. In one implementation, the angle may be about 45 degrees or135 degrees, for example.

The mutually additive portions H₂ and H₃ of a magnetic switching currentapplied to the MTJ that result from mutually aligned elongated top andbottom electrodes, assist the MTJ to switch states more quickly. Theswitching is quicker than would occur in response to the same switchingcurrent without assistance of the mutually additive portions H2 and H3.

FIG. 5 is a graph 500 illustrating a first plot 502 of switching timeversus switching current of an STT-MRAM configured according to anaspect of the present disclosure and a second plot 504 of switching timeversus switching current of conventional STT-MRAM that is assisted bymutually additive portions of a switching current induced magnetic fieldas disclosed herein. The first plot 502 and second plot 504, which arebased on a micro-magnetic model and Maxwell equations demonstrate asignificant reduction in switching time in the STT-MRAM that isconfigured according to aspects of the present disclosure for a givenswitching current. The graph 500 shows switching time in nanoseconds(ns) on the y-axis, and switching current in micro-amps (μA) on thex-axis. In one implementation, in which the mutually additive portionsH₂ and H₃ of the switching current induced magnetic field isperpendicular to the easy axis (e.g., FIGS. 2A and 2B), switching of theMTJ may be strongly assisted. Thus, switching may occur more quicklythan in the STT-MRAM implementation shown in FIGS. 3A and 3B in whichthe mutually additive portions H₂ and H₃ of the switching currentinduced magnetic field are parallel to the easy axis of the MTJ.

FIG. 6 is a process flow diagram illustrating a method 610 of making aSTT-MRAM according to an aspect of the present disclosure. In block 612,a first conductive layer is deposited and a first via is then arrangedon the lower conductive layer. In block 614, a first electrode isfabricated on the first via. In block 616, an MTJ is fabricated on thefirst electrode. The first electrode includes an elongated portionextending away from the MTJ. In block 618, a second electrode isdisposed on the MTJ. The top electrode includes an elongated portionextending away from the MTJ. In block 620, a second via is arranged onthe top electrode. A conductive layer is then deposited on the top via.

According to aspects of the present disclosure, an STT-MRAM design haslocal conductive interconnects, including electrodes, configured tocontrol the STT-MRAM current path and the magnetic field distribution toassist the spin logic switching process during band-to-band tunneling.An STT-MRAM design uses an internal STT-MRAM switching current togenerate a self-induced magnetic field to assist the spin logicswitching process so there is no need to use a separate current sourceor an external magnetic field. These approaches lead to the reduction ofthe spin-transfer torque switching time and lower switching powerconsumption, which results in improved efficiency and performance.

An aspect of the present disclosure includes an apparatus that includesa means for magnetically storing charge, a first means for conductingand a second means for conducting. The means for magnetically storingcharge may be, for example, the MTJ 210, the MTJ 310 and/or the MTJ 410.The first means for conducting may be, for example, the top electrode206, the top electrode 306 and/or the top electrode 406. The secondmeans for conducting may be, for example, the bottom electrode 212, thebottom electrode 312 and/or the bottom electrode 412.

The first means for conducting includes a first means for directing amagnetic field that extends laterally away from the means formagnetically storing charge. The first means for directing magneticfield may be, for example, the elongated portion 205, the elongatedportion 305 and/or the elongated portion 405.

The second means for conducting includes a second means for directing amagnetic field that extends laterally away from the means formagnetically storing charge. The second means for directing the magneticfield may be, for example, the elongated portion 211, the elongatedportion 311 and/or the elongated portion 411.

In another configuration, the aforementioned means may be any module orany apparatus configured to perform the functions recited by theaforementioned means. Although specific means have been set forth, itwill be appreciated by those skilled in the art that not all of thedisclosed means are required to practice the disclosed configurations.Moreover, certain well known means have not been described, to maintainfocus on the disclosure.

FIG. 7 is a block diagram showing an exemplary wireless communicationsystem 700 in which an aspect of the disclosure may be advantageouslyemployed. For purposes of illustration, FIG. 7 shows three remote units720, 730, and 750 and two base stations 740. It will be recognized thatwireless communication systems may have many more remote units and basestations. Remote units 720, 730, and 750 include IC devices 725A, 725Cand 725B that include the disclosed STT-MRAM devices. It will berecognized that other devices may also include the disclosed STT-MRAMdevices, such as the base stations, switching devices, and networkequipment. FIG. 7 shows forward link signals 780 from the base station740 to the remote units 720, 730, and 750 and reverse link signals 790from the remote units 720, 730, and 750 to base stations 740.

In FIG. 7, remote unit 720 is shown as a mobile telephone, remote unit730 is shown as a portable computer, and remote unit 750 is shown as afixed location remote unit in a wireless local loop system. For example,the remote units may be mobile phones, hand-held personal communicationsystems (PCS) units, portable data units such as personal dataassistants, GPS enabled devices, navigation devices, set top boxes,music players, video players, entertainment units, fixed location dataunits such as meter reading equipment, or other devices that store orretrieve data or computer instructions, or combinations thereof.Although FIG. 7 illustrates remote units according to the teachings ofthe disclosure, the disclosure is not limited to these exemplaryillustrated units. Aspects of the disclosure may be suitably employed inmany devices which include the disclosed STT-MRAM devices.

FIG. 8 is a block diagram illustrating a design workstation used forcircuit, layout, and logic design of a semiconductor component, such asthe STT-MRAM devices disclosed above. A design workstation 800 includesa hard disk 801 containing operating system software, support files, anddesign software such as Cadence or OrCAD. The design workstation 800also includes a display 802 to facilitate design of a circuit 810 or asemiconductor component 812 such as a one time programming (OTP)apparatus. A storage medium 804 is provided for tangibly storing thecircuit design 810 or the semiconductor component 812. The circuitdesign 810 or the semiconductor component 812 may be stored on thestorage medium 804 in a file format such as GDSII or GERBER. The storagemedium 804 may be a CD-ROM, DVD, hard disk, flash memory, or otherappropriate device. Furthermore, the design workstation 800 includes adrive apparatus 803 for accepting input from or writing output to thestorage medium 804.

Data recorded on the storage medium 804 may specify logic circuitconfigurations, pattern data for photolithography masks, or mask patterndata for serial write tools such as electron beam lithography. The datamay further include logic verification data such as timing diagrams ornet circuits associated with logic simulations. Providing data on thestorage medium 804 facilitates the design of the circuit design 810 orthe semiconductor component 812 by decreasing the number of processesfor designing semiconductor wafers.

For a firmware and/or software implementation, the methodologies may beimplemented with modules (e.g., procedures, functions, and so on) thatperform the functions described herein. A machine-readable mediumtangibly embodying instructions may be used in implementing themethodologies described herein. For example, software codes may bestored in a memory and executed by a processor unit. Memory may beimplemented within the processor unit or external to the processor unit.As used herein the term “memory” refers to types of long term, shortterm, volatile, nonvolatile, or other memory and is not to be limited toa particular type of memory or number of memories, or type of media uponwhich memory is stored.

If implemented in firmware and/or software, the functions may be storedas one or more instructions or code on a computer-readable medium.Examples include computer-readable media encoded with a data structureand computer-readable media encoded with a computer program.Computer-readable media includes physical computer storage media. Astorage medium may be an available medium that can be accessed by acomputer. By way of example, and not limitation, such computer-readablemedia can include RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage or other magnetic storage devices, orother medium that can be used to store desired program code in the formof instructions or data structures and that can be accessed by acomputer; disk and disc, as used herein, includes compact disc (CD),laser disc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveshould also be included within the scope of computer-readable media.

In addition to storage on computer readable medium, instructions and/ordata may be provided as signals on transmission media included in acommunication apparatus. For example, a communication apparatus mayinclude a transceiver having signals indicative of instructions anddata. The instructions and data are configured to cause one or moreprocessors to implement the functions outlined in the claims.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the technologyof the disclosure as defined by the appended claims. For example,relational terms, such as “top” and “bottom” are used with respect to asubstrate or electronic device. Of course, if the substrate orelectronic device is inverted, top becomes bottom, and vice versa.Additionally, if oriented sideways, top and bottom may refer to sides.Moreover, the scope of the present application is not intended to belimited to the particular configurations of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the correspondingconfigurations described herein may be utilized according to the presentdisclosure. Accordingly, the appended claims are intended to includewithin their scope such processes, machines, manufacture, compositionsof matter, means, methods, or steps.

What is claimed is:
 1. A method of constructing a magnetic memory cellcomprising: patterning a first electrode; coupling a first via to thefirst electrode; fabricating a magnetic tunnel junction (MTJ) comprisinga plurality of MTJ layers on the first electrode so that the firstelectrode has a first elongated portion extending laterally away fromthe MTJ by a sufficient lateral displacement to cause an MTJ switchingcurrent to flow in a first plane parallel the plurality of MTJ layers inthe first electrode; patterning a second electrode on the MTJ so thatthe second electrode has a second elongated portion extending laterallyaway from the MTJ by a sufficient lateral displacement to cause the MTJswitching current to flow in a second plane parallel the plurality ofMTJ layers in the first electrode; coupling a second via to the secondelectrode, in which a portion of the MTJ is directly between the firstvia and the second via; and controlling a switching current inducedmagnetic field by configuring the first elongated portion and the secondelongated portion to direct mutually additive portions of the switchingcurrent induced magnetic field through the MTJ.
 2. The method of claim1, further comprising: depositing a first conductive layer coupled tothe first electrode; and depositing a second conductive layer coupled tothe second electrode.
 3. The method of claim 2, in which: the first viais coupled between the first conductive layer and the first electrode;and the second via is coupled between the second conductive layer andthe second electrode.
 4. The method of claim 1, further comprising:defining an easy axis with respect to the MTJ; and configuring the firstelongated portion and the second elongated portion to induce theswitching current induced magnetic field parallel to the easy axis ofthe MTJ.
 5. The method of claim 1, further comprising: defining an easyaxis with respect to the MTJ; and configuring the first elongatedportion and the second elongated portion to induce the switching currentinduced magnetic field perpendicular to the easy axis of the MTJ.
 6. Themethod of claim 1, further comprising: defining an easy axis withrespect to the MTJ; and configuring the first elongated portion and thesecond elongated portion to induce the switching current inducedmagnetic field at an angle to the easy axis of the MTJ.
 7. The method ofclaim 1, in which the first electrode and the second electrode havesubstantially a same pattern.
 8. The method of claim 1, furthercomprising integrating the magnetic memory cell into a mobile phone, aset top box, a music player, a video player, an entertainment unit, anavigation device, a computer, a hand-held personal communicationsystems (PCS) unit, a portable data unit, and/or a fixed location dataunit.
 9. A method of constructing a magnetic memory cell comprising: thestep for patterning a first electrode; the step for coupling a first viato the first electrode; the step for fabricating a magnetic tunneljunction (MTJ) comprising a plurality of MTJ layers on the firstelectrode so that the first electrode has a first elongated portionextending laterally away from the MTJ by a sufficient lateraldisplacement to cause a switching current to flow in a first planeparallel the plurality of MTJ layers in the first electrode; the stepfor patterning a second electrode on the MTJ so that the secondelectrode has a second elongated portion extending laterally away fromthe MTJ by a sufficient lateral displacement to cause the switchingcurrent to flow in a second plane parallel the plurality of MTJ layersin the first second; the step for coupling a second via to the secondelectrode, in which a portion of the MTJ is directly between the firstvia and the second via; and the step for controlling a switching currentinduced magnetic field by configuring the first elongated portion andthe second elongated portion to direct mutually additive portions of aswitching current induced magnetic field through the MTJ.
 10. The methodof claim 9, further comprising: the step for depositing a firstconductive layer coupled to the first electrode; and the step fordepositing a second conductive layer coupled to the second electrode.11. The method of claim 10, in which: the first via is coupled betweenthe first conductive layer and the first electrode; and the second viais coupled between the second conductive layer and the second electrode.12. The method of claim 9, further comprising: the step for defining aneasy axis with respect to the MTJ; and the step for configuring thefirst elongated portion and the second elongated portion to induce theswitching current induced magnetic field parallel to the easy axis ofthe MTJ.
 13. The method of claim 9, further comprising: the step fordefining an easy axis with respect to the MTJ; and the step forconfiguring the first elongated portion and the second elongated portionto induce the switching current induced magnetic field perpendicular tothe easy axis of the MTJ.
 14. The method of claim 9, further comprising:the step for defining an easy axis with respect to the MTJ; and the stepfor configuring the first elongated portion and the second elongatedportion to induce the switching current induced magnetic field at anangle to the easy axis of the MTJ.
 15. The method of claim 9, in whichthe first electrode and the second electrode have substantially a samepattern.
 16. The method of claim 9, further comprising integrating themagnetic memory cell into a mobile phone, a set top box, a music player,a video player, an entertainment unit, a navigation device, a computer,a hand-held personal communication systems (PCS) unit, a portable dataunit, and/or a fixed location data unit.
 17. A method of constructing amagnetic memory cell comprising: depositing a first conductive layer;arranging a first contact via on the first conductive layer; fabricatinga first electrode on the first contact via; fabricating an MTJ on thefirst electrode, in which the first electrode includes a first elongatedportion extending away from the MTJ; fabricating a second electrode onthe MTJ, in which the second electrode includes a second elongatedportion extending away from the MTJ; arranging a second contact via onthe second electrode, in which a portion of the MTJ is directly betweenthe first contact via and the second contact via; and depositing aconductive layer on the second contact via.
 18. The method of claim 17,further comprising arranging a lateral displacement between the firstelongated portion and the second elongated portion relative to the MTJto direct mutually additive portions of a switching current inducedmagnetic field through the MTJ.
 19. The method of claim 17, furthercomprising: aligning the second contact via with the first contact viaand the portion of MTJ disposed directly between the first contact viaand the second contact via to direct a first portion of a magnetic fieldinduced by the MTJ from the first contact via through the MTJ; andarranging a lateral displacement between the second elongated portionand the MTJ to direct a second portion of the magnetic field induced bythe MTJ and the second contact via, the second portion of the magneticfield adding with the first portion of the magnetic field to enhance themagnetic field through the MTJ.
 20. The method of claim 17, furthercomprising integrating the magnetic memory cell into a mobile phone, aset top box, a music player, a video player, an entertainment unit, anavigation device, a computer, a hand-held personal communicationsystems (PCS) unit, a portable data unit, and/or a fixed location dataunit.